On May 29, 2016 2:18 AM, "Francisco Jerez" <curroje...@riseup.net> wrote: > > Jason Ekstrand <ja...@jlekstrand.net> writes: > > > On Fri, May 27, 2016 at 7:05 PM, Francisco Jerez <curroje...@riseup.net> > > wrote: > > > >> This fixes the few code quality regressions from the previous series > >> enabling SIMD32 CS codegen in the back-end -- AFAICT by the end of the > >> series we can finally enable GL 4.3 on all Gen8+ hardware. > >> > >> Patches 1-8 delay the SIMD lowering pass after the bulk of > >> optimization passes have been run, which should decrease the > >> compilation time of mainly SIMD32 shaders and improve the code quality > >> of SIMD32 shaders on all generations and shaders of any dispatch width > >> on older generations (up to and including IVB) that use SIMD lowering > >> more intensively to implement various workarounds. > >> > >> Patches 9-14 rework the SIMD lowering pass to avoid emitting the copy > >> instructions used to zip and unzip register regions where possible, > >> since the register coalesce and copy propagation passes seem to > >> perform rather poorly at getting rid of them in some cases. In the > >> long term we'll likely want to improve the register coalesce pass > >> irrespective of these changes. > >> > >> Patches 15-20 improve the compute-to-mrf pass used on Gen4-6 to handle > >> cases where the source of a VGRF-to-MRF copy is initialized by the > >> shader using multiple single-GRF writes, which becomes far more common > >> with the additional SIMD lowering going on after this series. > >> > >> Patches 21-24 are some other assorted changes improving code quality > >> on older gens. > >> > >> I wanted to provide more detailed (e.g. per commit) shader-db stats > >> with this series, but kind of ran out of time. Let me know if you > >> would like to see more evidence that any of the changes below is > >> improving code quality in case it's not clear from the commit alone. > >> > >> [PATCH 01/25] i965/fs: Let CSE handle logical sampler sends as expressions. > >> [PATCH 02/25] i965/fs: Allow constant propagation into logical send > >> sources. > >> [PATCH 03/25] i965/fs: Add FS_OPCODE_FB_WRITE_LOGICAL to > >> has_side_effects(). > >> [PATCH 04/25] i965/fs: Run SIMD and logical send lowering after the > >> optimization loop. > >> [PATCH 05/25] i965/fs: Take opt_redundant_discard_jumps out of the > >> optimization loop. > >> [PATCH 06/25] i965/fs: Fix UB list sentinel dereference in > >> opt_sampler_eot(). > >> [PATCH 07/25] i965/fs: Implement opt_sampler_eot() in terms of logical > >> sends. > > > > [PATCH 08/25] SQUASH: i965/fs: Add basic dataflow check to > >> opt_sampler_eot(). > >> > > > > > >> [PATCH 09/25] i965/fs: Refactor offset() into a separate function taking > >> the width as argument. > >> [PATCH 10/25] i965/fs: Generalize regions_overlap() from copy propagation > >> to handle non-VGRF files. > >> [PATCH 11/25] i965/fs: Factor out region zipping and unzipping from the > >> SIMD lowering pass. > >> [PATCH 12/25] i965/fs: Skip SIMD lowering source unzipping for regular > >> scalar regions. > >> [PATCH 13/25] i965/fs: Skip SIMD lowering destination zipping if possible. > >> [PATCH 14/25] i965/fs: Reindent emit_zip(). > >> > > > > 9-14 Reviewed-by: Jason Ekstrand <ja...@jlekstrand.net> > > > > > >> [PATCH 15/25] i965/fs: Teach regions_overlap() about COMPR4 MRF regions. > >> [PATCH 16/25] i965/fs: Simplify and improve accuracy of compute_to_mrf() > >> by using regions_overlap(). > >> [PATCH 17/25] i965/fs: Fix compute-to-mrf VGRF region coverage condition. > >> [PATCH 18/25] i965/fs: Refactor compute_to_mrf() to split search and > >> rewrite into separate loops. > >> [PATCH 19/25] i965/fs: Teach compute_to_mrf about the COMPR4 address > >> transformation. > >> [PATCH 20/25] i965/fs: Extend compute_to_mrf() to coalesce VGRFs > >> initialized by multiple single-GRF writes. > >> [PATCH 21/25] i965/fs: Extend remove_duplicate_mrf_writes() to handle > >> non-VGRF to MRF copies. > >> > > > > 15-21 scare me. A lot. They even make me think that forking the compiler > > between SNB and IVB may be a good idea. :-/ MRFs are annoying, but COMPR4 > > is such a gross hack that I really want to teach as little of the compiler > > about it as possible. > > > Heh, my impression (from writing the patches) is that COMPR4 was the > easiest part of it, it's not entirely unlike the usual Align1 source > regions -- with hard-wired width and vstride. I agree it's kind of a > gross hardware feature but all it took to handle it in compute-to-mrf > was some simple arithmetic [it would get slightly more complex if > compute-to-mrf attempted to handle COMPR4 LOAD_PAYLOAD instructions, but > I don't think it would necessarily be an insane idea].
I'll take another look on Monday or Tuesday. They're probably fine of I just read the original code and get sufficiently scared of that too. :-p > Honestly, what made patches 16-20 really hard to write (and maybe also > hard to review, I don't know), was disentangling the highly > special-cased and dubious dataflow logic of the compute-to-mrf pass > (patches 16 and 17 could qualify as bugfixes...), and that had little to > do with COMPR4 or even with MRFs. Compute-to-mrf is a crappy register > coalescing pass that can only handle a small subset of the cases where > one could possibly elide VGRF-to-MRF copies. > > My suspicion is that the situation would improve (both in terms of code > generation quality on MRF platforms and codebase maintainability) if > instead of forking the driver we got rid of the compute-to-mrf pass > altogether and used the normal register coalesce pass to coalesce VGRFs > into MRFs (since the one difficult part about coalescing registers is > working out the dataflow and variable interference, COMPR4 is just the > surface). > > BTW, do you have any objection against PATCH 21? It should be fully > independent from the other MRF-related ones. I didn't spend enough time on that one to say. I'll look at it next week. > > So here's the million dollar question: Do we need them? and, more > > importantly, do we need them now? I didn't see anything wrong in my brief > > skimming but don't call that a review. > > > *Shrug*, nothing in this series is strictly necessary [heh, except of > course PATCH 25 ;)], but if we don't include them the overall shader-db > balance from the whole series (including parts 1-4 except for patches > 16-20 from this series) on SNB would be: > > total instructions in shared programs: 5721434 -> 5755717 (0.60%) > instructions in affected programs: 2402892 -> 2437175 (1.43%) > helped: 1284 > HURT: 12148 > > instead of the following (not excluding any changes): > > total instructions in shared programs: 5721284 -> 5708369 (-0.23%) > instructions in affected programs: 489340 -> 476425 (-2.64%) > helped: 1398 > HURT: 21 > > > > >> [PATCH 22/25] i965/fs: Fix constant combining for instructions that cannot > >> accept source mods. > >> [PATCH 23/25] i965/fs: Allow scalar source regions on SNB math > >> instructions. > >> [PATCH 24/25] i965/fs: Skip gen4 pre/post-send dependency workaronds for > >> the first/last block. > >> [PATCH 25/25] i965: Expose GL 4.3 on Gen8+. > >> > > > > 22-25 are Reviewed-by: Jason Ekstrand <ja...@jlekstrand.net> > > > > Thanks. > > > > >> _______________________________________________ > >> mesa-dev mailing list > >> mesa-dev@lists.freedesktop.org > >> https://lists.freedesktop.org/mailman/listinfo/mesa-dev > >>
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